PHILADELPHIA, PA.- Most art lovers appreciate Philadelphia's importance to cultural and historical preservation, although its conservatory role extends beyond its borders.

It is embodied not only in the city's museums, universities and galleries, but also in the office of an institution no less significant to area residents: the Federal Bureau of Investigation.

"They represent icons of cultural history," Special Agent Robert K. Wittman said of the $225 million worth of art items he's played a role in recovering over his 20 years as in the bureau. He serves as the FBI's top investigator and coordinator in cases involving art theft and art fraud and works with the Violent Crimes Task Force at the FBI Regional Field Office.

Born in Baltimore in 1955, Mr. Wittman developed a fascination with art growing up the son of antiques storeowners. A man of cheerful countenance, he continues to love visual artworks, particularly the works of Monet as well as the countryside and the seascapes of Renoir. He admires the impressionists most of all but enjoys masters of other stripes like Picasso.

Herb Lottier, director of protection services at the Philadelphia Museum of Art and a retired Philadelphia Police captain, describes the special agent, with whom he has worked closely, as an unfailingly jovial presence.

"He's an entertainer as well as an investigator - the best of both worlds," Mr. Lottier said. "He has the right outlook on life."

Although Mr. Wittman plans to retire in September and thereafter work as a consultant to art security firms, he could certainly have imagined a duller living than safeguarding cultural treasures for future generations.

He conducted his first major art-recovery operations in 1988. That year, a bandit stole a crystal ball that once belonged to the Empress Dowager Cixi from the Asian wing of the University of Pennsylvania Museum of Archaeology and Anthropology in the middle of the night. The centerpiece of the museum, it is the second largest crystal ball in the world.

Also in 1988, a robber had stolen Auguste Rodin's 1860s piece "Man With a Broken Nose" from the Rodin Museum on Benjamin Franklin Parkway. The piece turned up under a hot-water heater on Pine Street.

After helping retrieve both pieces, Mr. Wittman's bosses at the FBI decided he'd be the right person to put in charge of art crime investigations. The bureau paid for his formal arts training and now the agent lectures across the world to museums, art institutes and law enforcement agencies. He has spoken at the American Association of Museums Annual Conference and the International Conference on Cultural Property Protection in Cuzco, Peru.

The cases he handled since only heightened in profile and broadened in geographic scope. One afternoon in Dec. 2000, armed and masked thieves took two Renoirs and a famous Rembrandt self-portrait from the Swedish National Museum in Stockholm.

A team of Swedish and American agents led by Mr. Wittman met with four men in possession of the Rembrandt, valued at $36 million, at a hotel in Copenhagen, Denmark. Posing as buyers, they offered to purchase the painting and arrested the four - two Iraqis, a Gambian and a Swede.

But why help solve art-theft cases for foreign governments? Mr. Wittman explains that because of the intricacies of international cultural crime, American authorities can draw important connections to domestic cases, build relationships with foreign agencies and find leads on investigations into other illicit commerce.

"Art belongs to the whole world," he said. "[These other countries] are our partners and that crosses over into other crimes we would investigate together. It just fosters that strong relationship."

Art investigations sometimes yield more recovered items than the authorities expect. After an armed daytime robbery deprived a Zimbabwe museum of tribal masks dating back hundreds of years, a group of Polish and American agents organized a sting operation in Warsaw, Poland. Mr. Wittman portrayed himself to the thieves as an African art dealer, proceeded with the arrests and repossessed a cache of stolen items from various international galleries including masks, diamonds, elephant tusks and other ivory carvings.

Among the most prominent cases the agent has handled was the retrieval of one of the original 14 copies of the Bill of Rights in 2003. That year, a family who possessed the document for over a century had offered to sell it to the newly founded National Constitution Center.

During the authentication process, the FBI discovered it to have been stolen from the statehouse in South Carolina in 1865 by one of Gen. William Tecumseh Sherman's soldiers. The family that had kept the document tried repeatedly to sell it back to South Carolina, but the state continued to insist it would not buy stolen property.

Now the fourth largest international crime in the world, art theft has only become more widespread in recent years as many works have appreciated in value. And it has been a particularly pronounced issue in a major cultural center like Philadelphia. Bureau agents here continue their investigation into the theft of John A. Woodside's 1840s painting "Fairmount Water Works," estimated to be worth $75,000, from the Philadelphia Park Systems office at 1515 Arch St.

"Unfortunately, Philadelphia has had its share of museum art theft," Mr. Wittman said.

About nine out of 10 of the theft cases on which he works involve undercover service. As someone with virtually optimum proficiency in matters of both culture and law enforcement, agencies abroad find him a man of extreme utility, FBI Special Agent John Kitzinger said.

Mr. Kitzinger oversees the task force alongside which Mr. Wittman works. As art crime won't slow down for Mr. Wittman's departure, the task force head is grateful his colleague will remain nearby to provide assistance.

"He's going to make it easy for us because he's not going anywhere," Mr. Kitzinger said. "Bob's always going to be available. We can always draw on his expertise."

Left in place will be a team of 13 agents formed in 2005 with Mr. Wittman as its original leader. Mr. Lottier said he has every confidence in the team's ability to carry on its duties even as he's sad to see the special agent go.

"It'll be a serious loss for the area, particularly the Philadelphia area, as well as nationally," Mr. Lottier said. "But life goes on. He's left a good team in place. He's leaving us in very, very capable hands."

Special Agent in Charge Janice Fedarcyk said once Mr. Wittman leaves, another agent will step into his position after undergoing arts training. John Hess is one special agent the bureau is acquainting with many of Mr. Wittman's duties as an art investigator and who may take over his senior agent's work in full, she said.